FOSSIL BIRDS. 537 



While in former times existing birds were divided into a 

 Jarge number of " orders," these are now known to be sub- 

 divisions of the two sub-classes Ratitce and Carinata, and 

 probably in many cases should be honored only with the rank 

 of sub-orders. The discovery of the ArcJiceopteryx and of 

 birds with teeth and biconcave vertebrae has essentially mod- 

 ified prevailing views as to the classification of birds. 



Sub-class 1. Saururce. The oldest bird, geologically 

 speaking, is the Arcliceopteryx (Fig. 460) of the Jurassic 

 slates of Solenhofen, Germany. This was a bird about the 

 size of a crow, the tail being 22 cent. (8-9 inches) long, but 

 longer than the body, supported by many movable vertebrae 



Fig. 460. Restoration of ArcJuwpteryx macrura. After Owen, from Nicholson. 



and covered with feathers in distichous series, not in the 

 shape of a fan. The jaw-bones were long, and contained 

 conical teeth. The head, shoulder girdle, and fore limbs, 

 with their three digits, were reptilian in form. (Vogt.) In 

 these respects and in the long tail the creature served as a 

 connecting link between the reptiles, such as the bird-like 

 Compsognatlius, and the existing birds. The hind legs and 

 wings have the ordinary bird structure, though .the metacar- 

 pal bones were not co-ossified; the foot consisted of three digits. 

 Sub-class 2. Odontornithes* Still other connecting links 

 between the reptiles and birds has been discovered by Marsh 

 * Of these the Ichthyornis was probably the ancestor of the gulls, 

 and the Hesperornis of the grebes aud loons (Parker). 



